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Galaxy Stellar Mass Assembly Between 0.2 < z < 2 from the S-COSMOS Survey

Ilbert, O. and Salvato, M. and Le Floc'h, E. and Aussel, H. and Capak, P. and McCracken, H. J. and Mobasher, B. and Kartaltepe, J. and Scoville, N. and Sanders, D. B. and Arnouts, S. and Bundy, K. and Cassata, P. and Kneib, J.-P. and Koekemoer, A. and Le Fèvre, O. and Lilly, S. and Surace, J. and Taniguchi, Y. and Tasca, L. and Thompson, D. and Tresse, L. and Zamojski, M. and Zamorani, G. and Zucca, E. (2010) Galaxy Stellar Mass Assembly Between 0.2 < z < 2 from the S-COSMOS Survey. Astrophysical Journal, 709 (2). pp. 644-663. ISSN 0004-637X.

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We follow the galaxy stellar mass assembly by morphological and spectral type in the COSMOS 2 deg^2 field. We derive the stellar mass functions and stellar mass densities from z = 2 to z = 0.2 using 196,000 galaxies selected at F_(3.6 μm) > 1 μJy with accurate photometric redshifts (σ_[(zphot−zspec)]/(1+zspec) = 0.008 at i^+ < 22.5). Using a spectral classification, we find that z ~ 1 is an epoch of transition in the stellar mass assembly of quiescent galaxies. Their stellar mass density increases by 1.1 dex between z = 1.5-2 and z = 0.8-1 (Δt ~ 2.5 Gyr), but only by 0.3 dex between z = 0.8-1 and z ~ 0.1 (Δt ~ 6 Gyr). Then, we add the morphological information and find that 80%-90% of the massive quiescent galaxies (logM ~ 11) have an elliptical morphology at z < 0.8. Therefore, a dominant mechanism links the shutdown of star formation and the acquisition of an elliptical morphology in massive galaxies. Still, a significant fraction of quiescent galaxies present a Spi/Irr morphology at low mass (40%-60% at logM ~ 9.5), but this fraction is smaller than predicted by semi-analytical models using a "halo quenching" recipe. We also analyze the evolution of star-forming galaxies and split them into "intermediate activity" and "high activity" galaxies. We find that the most massive "high activity" galaxies end their high star formation rate phase first. Finally, the space density of massive star-forming galaxies becomes lower than the space density of massive elliptical galaxies at z < 1. As a consequence, the rate of "wet mergers" involved in the formation of the most massive ellipticals must decline very rapidly at z < 1, which could explain the observed slow down in the assembly of these quiescent and massive sources.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ilbert, O.0000-0002-7303-4397
Salvato, M.0000-0002-4314-8713
McCracken, H. J.0000-0002-9489-7765
Scoville, N.0000-0002-0438-3323
Koekemoer, A.0000-0002-6610-2048
Surace, J.0000-0001-7291-0087
Additional Information:© 2010 American Astronomical Society. Print publication: Issue 2 (2010 February 1); received 2009 January 6; accepted for publication 2009 December 4; published 2010 January 6. We are grateful to the referee for his/her careful reading of the manuscript and his/her useful suggestions. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1278386 issued by JPL. We gratefully acknowledge the contributions of the entire COSMOS collaboration consisting of more than 100 scientists. The HST COSMOS program was supported through NASA grant HST-GO- 09822. More information on the COSMOS survey is available at
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: luminosity function, mass function
Record Number:CaltechAUTHORS:20100209-115745637
Persistent URL:
Official Citation:Galaxy Stellar Mass Assembly Between 0.2 < z < 2 from the S-COSMOS Survey O. Ilbert, M. Salvato, E. Le Floc'h, H. Aussel, P. Capak, H. J. McCracken, B. Mobasher, J. Kartaltepe, N. Scoville, D. B. Sanders, S. Arnouts, K. Bundy, P. Cassata, J.-P. Kneib, A. Koekemoer, O. Le Fèvre, S. Lilly, J. Surace, Y. Taniguchi, L. Tasca, D. Thompson, L. Tresse, M. Zamojski, G. Zamorani, and E. Zucca 2010 ApJ 709 644-663 doi: 10.1088/0004-637X/709/2/644
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17436
Deposited By: Jason Perez
Deposited On:10 Feb 2010 21:17
Last Modified:28 Feb 2018 20:10

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